Conventionally, cytoanalyzers, which allow the operator to set fraction areas on a two-dimensional distribution chart by using a keyboard, have been known. For example, a cytoanalyzer disclosed in Japanese Patent Application Laid-Open No. 5-60752 is listed as the cytoanalyzer of this type. In the cytoanalyzer of this type, the operator is allowed to manually set a fraction area used for discriminating specific cells such as lymphatic corpuscles from the other cells on a two-dimensional distribution chart that indicates the intensities of forward and sideward scattered light rays, and with respect to cells included in the fraction area thus set, an analyzing process for fluorescent characteristics is carried out.
Therefore, in the cytoanalyzer, in order to accurately analyze the fluorescent characteristics of specific cells such as lymphatic corpuscles, accurately setting the fraction area is prerequisite for the analyzing process. Here, in order to accurately set the fraction area, it is necessary for the operator to distinguish an area in which specific cells such as lymphatic corpuscles are present from areas in which the other cells are present.
In the above-mentioned two-dimensional distribution chart, scattered light intensities possessed by respective cells are determined, and with respect to each of the cells, a dot indicating the cell is put on a position corresponding to the scattered light intensity possessed by the cell on a plane so that the chart is formed. Thus, the two-dimensional distribution chart is allowed to indicate the presence or absence of a cell that has a predetermined scattered light intensity. In this arrangement, however, when a plurality of cells have the same scattered light intensity, these cells are represented by a single dot. In other words, the two-dimensional distribution chart fails to indicate the number of cells that have a predetermined scattered light intensity. Consequently, when the operator is only allowed to view the two-dimensional distribution chart, the operator cannot accurately confirm the distribution state of cells. The above-mentioned cytoanalyzer is designed in such a manner that the operator sets a fraction area based upon only the two-dimensional distribution chart of this type; therefore, the operator tends to fail to accurately confirm the distribution state of the cells and consequently fail to set an accurate fraction area.
As described above, in the above-mentioned cytoanalyzer, the operator manually sets a fraction area on a two-dimensional distribution chart. As described in the above-mentioned Japanese Patent Application Laid-Open No. 5-60752, when a plurality of groups of dots indicating cells (groups b, c and d in FIG. 5(a) of the above-mentioned gazette) are placed in a separate manner on the two-dimensional distribution chart, the operator is allowed to set a fraction area; however, when a plurality of groups thereof are placed close to one another, the operator cannot discriminate the respective groups. Consequently, in this case also, the operator cannot set an accurate fraction area.